Prerelease Version 0.5.0-rc1

Pre-release for version 0.5.0

Changes:

cad771d - add R^2 to validation tool
180d711 - add pFIRE-ShIRT cross-validation tool
4c91cce - improve config error handling
deaa270 - add FP trapping to condition number calculation
51df059 - add mutual information convergence criterion
9db4dc0 - Update README.md